[vm/ffi] fromFunction and asFunction drop type argument and return dynamic

[dcharkes]

No description provided.

[sjindel-google]

Can you please clarify the title/description of the task?

I'm not sure if you're identifying a bug or feature.

[dcharkes]

If I remember correctly, we created this task during a discussion about the API. I think the goal was to remove locations in the source code which are invariant/covariant/contravariant. By removing the type argument from asFunction() it becomes invariant by construction (but dynamically typed).

For fromFunction I don't remember what we discussed.

If there is a bug in variance checking for fromFunction and asFunction then this should be classified as bug. Though a bug could also be fixed without changing the API.

Edit: see #37385

[sjindel-google]

Ah yes, #37853 is the bug and this is the API cleanup.

[dcharkes]

This is a trade-off between verbosity and static checking. Removing the type argument to asFunction and lookupFunction makes it less verbose. However, it also makes it so that type errors are only caught when assigning the returned closure to a variable with some function signature.

/cc @mkustermann what do you think?

[sjindel-google]

We agreed offline to leave it as is.